Voltage reg

[Rod]

i need plans for a regulator that will turn 12 volts into 7.2..also a safety just incase the regulator packs up and sends 12 volts frying my circuit...if some one could help...need it to be easy to make and as cheap as possible

thanks
rod

[Carl]

Re: Voltage reg

How much current? How good a regulation? You can do something grungy with an opamp, zener, and a couple of resistors.

[rod]

Re: Voltage reg

DC current about 2amps and yes it has to have good reulation

[Carl]

Re: Voltage reg

2 amps... that's a lot. You need to drop 5 volts, thus the series device(s) needs to dissipate 10 watts. So you will probably need a heat sink. I can sketch up a basic regulator that will work fairly well, might have to wait til I get back home where I have a scanner.

- Carl

[rod]

Re: Voltage reg

THANKS CARL

[Carl]

Try this...




Here is a simple circuit that will do what you want. The opamp should be a single supply type like the LM358. The transistor should be a high-power type, TO220 case with a heat sink. The 2-ohm resistor is optional and should be a wire-wound 10 watt rated - it will reduce the power dissipated by the transistor and should provide short-circuit protection if the transistor goes south. The 240-ohm resistor can be made with (2) 120-ohm resistors.

What are you wanting to do, run a cordless drill off of a cigarette lighter?

[Robert Hoolko]

Re: Try this...

I should not speak up considering the mistakes I have made recently, but I get 6.2 v out.

Robert

[Carl]

Re: Try this...

Oops... you're right. The 120-ohm resistor should be 440-ohms, made with (2) 220-ohms in series. Thanks!

[Carl]

Oops again...

I meant the 240-ohm resistor should be 440... need more sleep...